Tips for making Mesh Rigid-body collision shapes more stable
Jittering objects are normally caused by the collision margin. See the documentation:

Collision Margin
The collision margin is used to improve performance and stability of rigid bodies. Depending on the shape, it behaves differently, some shapes embed it, while others have a visible gap around them:
The margin is embedded for these shapes:

Sphere
Box
Capsule
Cylinder
Convex Hull: Only allows for uniform scale when embedded.

The margin is not embedded for these shapes:

Cone
Active Triangle Mesh
Passive Triangle Mesh: Can be set to 0 most of the time.


And:

Simulation Stability
The simplest way of improving simulation stability is to increase the steps per second. However, care has to be taken since making too many steps can cause problems and make the simulation even less stable (if you need more than 1000 steps, you should look at other ways to improve stability).
Increasing the number of solver iterations helps making constraints stronger and also improves the object's stacking stability.
It's best to avoid small objects, as they're currently unstable. Ideally, objects should be at least 20 cm in diameter. If it's still necessary, setting the collision margin to 0, while generally not recommended, can help making small object behave more naturally.

Here's a quick example scene for you to inspect.